fix VEC3 16 bit indices support (remove false-positive assert)

src/coders/vec3.cpp

@@ -125,7 +125,6 @@ static model::Mesh load_mesh(
     if (flags == FLAG_ZLIB) {
         throw std::runtime_error("compression is not supported yet");
     }
-    assert(flags == 0);
     std::vector<VertexAttribute> attributes;
     for (int i = 0; i < attributeCount; i++) {
         attributes.push_back(load_attribute(reader));